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We thank Dr. Alfonso and colleagues for their interest in our vignette. Our meticulous comparison of the intravascular imaging and histology of a calcified nodule (CN) indicates the discrepancy of these findings, particularly for the presence of a red thrombus (1). The clinical significance of a CN with complete endothelial coverage is strikingly different from a large red thrombus formation. Such a CN without severe stenosis in nonculprit lesions may have a benign prognosis. Coronary intervention for a fully endothelialized CN could produce an “iatrogenic” complicated lesion. Therefore, we should pay attention to the interpretation of intravascular images and know the limitation of the diagnostic accuracy of optical coherence tomography (OCT) for thrombus formation within the coronary artery tree. A combination of imaging devices and close observation of the surrounding vessel wall could help the interpretation of these images.

Although it is widely accepted that a CN has the potential to develop a coronary thrombosis (2,3), the pathogenesis and microstructure of a CN are still a mystery. In our experience, a protruding calcified lesion of a coronary artery, which could be defined as a classic calcified nodule, always shows a fibrin-rich calcium-containing nodule. The superficial platelike calcification within the intima generally contains minimal fibrin deposition. The distinct histological features of a CN compared with nonnodular calcification suggests the differential etiology for these 2 types of calcification.

Examination of ex vivo imaging and histology by our serial autopsy cases identified tiny calcified nodules, which are exactly like the images in your previous presentation (4). These small CNs could interpret red luminal thrombus by OCT. We should be mindful that an irregular protruding bright mass with shadowing could represent a CN on OCT. Continuous effort to compare coronary imaging and histopathology of multifarious atherosclerotic lesions in human coronary arteries is recommended by both the pathologist and cardiologist.